Metallurgical grade ferroniobium alloys (FeNb) contain predominately iron and niobium and preferably more than 50% by weight niobium and most preferably 63% to 67% by weight niobium with the balance including iron and minor amounts of silicon and smaller amounts of aluminum, phosphorous and titanium. Ferroniobium and other such ferroalloys are relatively inert. For example, FeNb can withstand immersion in concentrated hydrochloric acid for prolonged periods of time without any apparent solubilization and leaching of its iron content. Likewise, it can withstand prolonged exposure to air at ambient temperatures with little or no weight gain.
Further, ferroniobium, while seemingly a good intermediate or starting material for the preparation of niobium compounds or niobium metal, has previously not been suitable for this purpose for several reasons. In addition to its non-reactive characteristics, it is also quite hard and, therefore, difficult to comminute into small enough particles to be commercially suitable for subsequent reaction schemes.
One possible solution to these drawbacks would be the formation of hydrogen containing compounds of ferroniobium or of its niobium content since hydrogen embrittlement is a well recognized phenomenon. The traditional method for hydriding Nb and Nb alloys has been to use high temperature and moderate pressures to facilitate hydrogen absorption. The absorption of hydrogen into iron and niobium has been discussed ("Metal Hydrides", Academic Press, New York and London, 1968, Nb pgs. 602-603, Fe pgs. 85, 627-628) with reference to temperatures of 400.degree. C. to 800.degree. C. and moderate pressures. Further work described in U.S. Pat. No. 4,440,737 discusses room temperature reaction of vanadium based alloys with hydrogen requiring pressures of 50-70 atm. Hydrogen storage systems involving ferrovanadium alloy are described in U.S. Pat. No. 4,318,897 which requires activation of the alloy using vacuums of the order of 10.sup.-3 Torr and temperatures of 600.degree. C. before room temperature hydride formation is conducted at 50 to 70 atmos.
These reactions are unattractive commercially as a starting point for methods of extracting values from ferrometal alloys.